The measurement of patient's respiration is useful in the monitoring and diagnosis of a wide range of respiratory disorders, as well as being a useful broader metric of a patient's condition. Measurements of interest may include respiratory rate (breaths per minute, BPM), flow, tidal volume, breathing pattern as well as changes in these over time.
Devices for monitoring breathing typically fall into 3 main categories:                i) those that observe the movement or tissue composition of the abdomen and/or chest,        ii) those that measure the flow of air, and        iii) those that measure concentrations of different gases in the blood or expired air        
Devices of type i) may involve the measuring of: transthoracic and abdominal impedance, a circumference through strain, pressure or fiber-optic gauges embedded in belts and straps, electrical activity of the muscles involved in breathing (electromyography). Several of these devices require the use of obtrusive constrictive belts placed around the chest and abdomen which may not be conducive to continuous or long term monitoring, particularly for patients with certain conditions. Other devices require expensive and complex infrastructure around the patient and/or require a stationary patient to take measurements since patient movement disrupts the measurements, which effectively precludes the ability for home monitoring.
Where a patient requires Oxygen therapy, this can interfere with certain devices of type ii) which measure nasal gas flow. Also, mouth breathing cannot be measured with devices such as a cannula. Furthermore, a device measuring total breathing gas flow, such as a face mask, may be obtrusive and uncomfortable for patients, thus limiting the ability for continuous or long term monitoring of measurements.
Devices of type iii) tend not to give a reliable indication of changes in tidal volume and may react slowly to disruptions in breathing. Such devices are often obtrusive and not conducive to continuous or long term or remote home monitoring.
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